With the trend of widely used wireless local area network (WLAN) applications, wireless communication products have piqued a global attention from almost all aspects. The antenna designs used for WLAN access points with high gain and omnidirectional radiation pattern have also gotten their role in development to response to the increasing demands. While providing a new antenna design with an improved functional gain, it is also required to consider the structure of the new design for a cost effective manufacturing process. The present invention thus yields a cost effective new antenna design to meet the practical need of WLAN applications.
Most existing antenna designs used for WLAN access points are either dipole or monopole as shown in FIG. 1. FIG. 1 is the structure of a traditional dipole antenna 100. This type of antenna can produce a good horizontal omnidirectional radiation pattern. Its practical use, however, has been restricted due to its complicated antenna structure and the limited receiver's gain of only 2.2 dBi. A Taiwan patent 529783, “Dipole Antenna Structure,” discloses an improved dipole antenna design, which enhances the antenna operating frequency and the bandwidth stability. This design of dipole antenna, however, has no advantage of antenna gain.
In 2002, Shor (U.S. Pat. No. 6,747,605 and US publication 2003/0020665) disclosed two similar designs of planar high frequency antenna. Both designs of antenna comprise a multi-dipole structure for both signal receiving and transmission. This multi-dipole antenna also comprises multiple sets of opposing layered conducting strips formed on the two sides of a substrate. In addition to the fact that it is a more complex design to distribute the whole antenna over a two-sided printed circuit board, this type of antenna also needs added chips for inductor or capacitor to achieve broader bandwidth and the compatible matching. The operating bandwidth of this type of antenna is between 5.15-5.35 GHz; its antenna gain is around 4.5 dBi; the antenna dimension is around 1.2 wavelengths (λ). To get higher gain of 7 dBi, the antenna dimension needs to be extended to 2.6 wave length (λ), which is too bulky for practical applications.
To overcome the drawback of the conventional antenna design with a complex structure and a limited gain of 2.2 dBi, the present invention provides a planar dipole antenna, which has three equal-phase current areas, with much higher gain of 6.8 dBi. The present invention is a single-sided circuitry design, which is a simple structure and can be easily formed on the dielectric substrate by a standard printing or etching process.